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Scientists want to control the quantum nature of light

Future quantum encryption for securing digital communication is just one of the areas that a new research project at the Department of Physics, Chemistry and Pharmacy will explore with the Semper Arden's grant from the Carlsberg Foundation.

By Majken Brahe Ellegaard Christensen, 2/21/2019

Light consist of small packages of energy, which are also called quanta. Physicists have known this for the past 100 years, but today it is still a mystery how to control these individual light particles.

Together with colleagues, researcher Sebastian Hofferberth will now examine the possibility of controlling light in his laboratory in Odense. Here, he combines ultracold atoms with high precision lasers into an experimental quantum optics setup to tame individual light particles also known as photons.

Will decrease the speed of light

Light moves through empty space with approx. 300,000 km/sec. When light moves through, for example, a window or a piece of plastic, it always moves slower. The light will never move faster, as this is an upper limit dictated by the laws of physics.

Exactly how slow the light moves depends on what the material is made of. It is exactly this characteristic that Hofferberth will use. Using quantum optics control techniques in a special material, he can lower the speed of light to a millionth of the speed in empty space.

When light travels at a lower speed, Hofferberth gets the opportunity to study how the light behaves in greater detail and to exert some control over it. But simply reducing its speed is not enough to make photons notice each other.

Atoms will act as a quantum magnifier

Normally, two photons do not interact with each other. This remains true also when they are very slow. As an additional second step in the planned experiments, Hofferberth will use a novel trick to change this. The photons will be coupled to so-called Rydberg atoms.

These Rydberg atoms are several thousand times larger than regular atoms, which makes them extremely sensitive. Harnessing this combination of extreme scales, gives Hofferberth a unique opportunity to examine the behavior of the light particles when they collide with each other.

Collaboration with Aarhus University

The project is called "Quantum Control of Light" and has just received DKK 15.2 million from the Carlsberg Foundation. Professor at Aarhus University, Thomas Pohl is the main applicant, and Sebastian Hofferberth is co-applicant and thus receives DKK 6.2 million of the total grant.

Read more about the project on the website of the Carlsberg Foundation.